NTSB Identification: SEA91LA139.
The docket is stored on NTSB microfiche number 44445.
Accident occurred Saturday, June 22, 1991 in CHALLIS, ID
Probable Cause Approval Date: 07/13/1993
Aircraft: CESSNA 180G, registration: N4700U
Injuries: 1 Minor,1 Uninjured.

NTSB investigators may not have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.

THE CESSNA 180 WAS IN CRUISE FLIGHT A FEW MINUTES AFTER DEPARTURE WHEN THE ENGINE BEGAN RUNNING ROUGH AND LOST POWER. THE PILOT WAS UNABLE TO RETURN TO A SAFE LANDING SITE, SO ELECTED TO ATTEMPT A FORCED LANDING NEAR A RIVER. AN ENGINE TEARDOWN REVEALED THAT THE EXHAUST VALVE ROCKER SHAFT BOSS ON ONE CYLINDER HAD FAILED AND THE BROKEN PIECE MIGRATED UNDER THE INTAKE ROCKER SHAFT, WHERE IT CAUSED THE VALVE PUSH ROD TO BEND.

The National Transportation Safety Board determines the probable cause(s) of this accident to be:

THAT THE PILOT ENCOUNTERED UNSUITABLE TERRAIN DURING A FORCED LANDING AFTER A POWER LOSS DUE TO A FRACTURED CYLINDER BOSS AND A BENT ENGINE PUSHROD.

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